Biology · Environmental Studies

Microbiology and Nitrogen Cycle

1,029 Questions

This hub focuses on microbiology and the nitrogen cycle, covering essential concepts about bacteria and soil microbes. Topics include nitrogen fixation, bacterial structures, and soil microbial processes. These concepts are frequently tested in general science sections of various competitive exams.

Nitrogen fixing bacteriaGram-positive bacteriaBacterial flagellaDenitrifying bacteriaAmmonia conversion processBacterial resting spores

Microbiology and Nitrogen Cycle Questions

Multiple choice

Azotobacter is

  1. phosphate solubilising bacteria

  2. symbiotic bacteria

  3. non-symbiotic bacteria

  4. gram positive bacteria
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Azotobacter is non-symbiotic bacteria.

Multiple choice

Bacteria having siderophores act as

  1. biofertilisers

  2. iron-chelation agents

  3. Both 1 and 2

  4. biopesticide
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Bacteria having siderophores act as both biofertilisers and iron-chelation agents.

Multiple choice

Which of the following organisms are distinguished by GeneXpert testing system?

  1. Acid fast from non-acid fast organisms

  2. NTM broad category microbes

  3. NTM from mycobacterium tuberculosis

  4. Mycobacterium tuberculosis from Nocardia
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

GeneXpert testing system distinguishes fairly well between NTMs and mycobacterium tuberculosis. NTMs (non-tuberculous mycobacteria) are emerging microbes that cause a spectrum of diseases including TB-like lung disease, localised infections of the lymphatic system, skin, soft tissue or bone and systemic disease.

Multiple choice

SOS repair for repairing mutation errors is used by which of the following?

  1. Pseudomonas aeruginosa

  2. E. coli

  3. Mycobacterium tuberculosis

  4. Bacillus subtilis
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The process by which E. coli repairs large amount of damage is called SOS repair. This process is not a single discrete mechanism. It involves a large number of responses. The ability to repair pyrimidine dimers, to shut off respiration, to delay septum formation and to induce prophages are a few examples. All the processes are well-coordinated.

Multiple choice

An example of free living nitrogen fixing aerobic bacteria is

  1. clostridium

  2. rhizobium

  3. azotobacter

  4. rhodospirillum
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Azotobacter is a free-living, aerobic, nitrogen-fixing bacteria found in soil. Unlike Rhizobium which forms symbiotic associations with legume roots, or Clostridium which is anaerobic, Azotobacter lives independently and fixes atmospheric nitrogen aerobically. Rhodospirillum is a photosynthetic bacteria, not primarily known for free nitrogen fixation.

Multiple choice

Which of the following is a free-living anaerobic nitrogen fixing bacteria?

  1. Clostridium

  2. Rhizobium

  3. Azotobacter

  4. Nitrobacter
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Clostridium is a free-living anaerobic nitrogen-fixing bacteria. It lives in soil and fixes nitrogen without requiring oxygen or a host plant. Rhizobium is symbiotic (requires legume host), Azotobacter is aerobic (requires oxygen), and Nitrobacter is a nitrifying bacteria that converts nitrite to nitrate but does not fix nitrogen.